There are many different types of sensors on the market, with each having specific capabilities, uses, and shortcomings. Two types of sensors that utilize optical components for sensing purposes are ambient light sensors and proximity sensors.
Ambient light sensors normally use a relatively small number of photosensitive pixels. In other words, the photosensitive area of an ambient light sensor is usually relatively small. Ambient light sensors are used in a number of applications such as mobile communication devices, laptops, Personal Digital Assistants, web cameras, imaging, photography, etc. As the name suggests, ambient light sensors are primarily used to measure or detect ambient light.
Proximity sensors, as compared to ambient light sensors, typically include a light source and a corresponding photodetector. The photodetector of a proximity sensor, not unlike the ambient light sensor, includes a number of photosensitive pixels. Proximity sensing (e.g., detecting a presence or proximity of an object near the sensor) involves transmitting light via the light source and then receiving light that reflects off an object-to-be-detected at the photodetector. The types of applications in which proximity sensors are used include mobile communication devices, industrial equipment, manufacturing equipment, touchless/sanitary devices, etc.